Return bend



Aug. 28, T928. 1,681,933

J. P. FISHER y RETURN BEND Filed April 20. 1920 Patented Aug. 2s, 192e.

uNlTEDr-sfrArEs 17,681,933 PATENT OFFICE.

JAMES P. FISHER, OF BARTLESVILLE, OKLAHOMA, .ASSIGNOR T DOHERTY RE- SEARCH COMPANY, OF-NEW YORK, N. Y.,

A CORPORATION 0F DELAWARE.

RETURN BEND.

Application led April 20, 1920.' Serial NQ. 375,213.

The present invention relates to a return bend for pipes, and more particularly to a return bend suitable for use on high pressure tubular oil stills or'in similar structures in which a fluid is heated to high temperatures and under high pressures.

In tubular stills of' the type mentioned above, the oil undergoing treatment is circulated under high pressure in a continuous l0 stream through a coil of pipe and heated, in a suitable furnace, to a high temperature. As the oil passes through the heated coil it is partly decomposed with the formation of some free carbon which usually deposits on l5 the inner walls of the coil and tends to fill and obstruct the passageway therethrough. When the carbon deposit becomes so thick that it interferes with the operation of the still, the circulation and hea-ting of the oil are discontinued and the carbon is removed. To permit the removal of the carbon, the coil is made up of a. number of straight lengths of heating pipe, extending through the furnace and projecting beyond the furnace Walls, and the ends, of adjacent pipes are connected, on the outside of the furnace, by means of removable return bends, so as to form a continuous coil.

The return bends are so arranged that they may be easily removed to give access to the interior of the tubes and to permit the removal of deposited carbon or sediment therefrom. The formation of a fluid tight joint between the removable return bends and the 35 pipe sections presents many difficulties however, since gaskets or packing or rubber or other suitable material decompose at temperatures to which the oil is heated and therefore cannot be used. Moreover, oil at the 4o temperatures and under the .pressures employed in the stills is very fluid and readily leaks through any small spaces or crevices which may be present in the joints. The inner surface of the joint, in addition, should be free of obstructions or projections which might interfere with the -flow of oil or promote the deposition of carbon in the tube.

The joint must also be of simple construction to permit being easily disconnected and reassembled.

The'object of the present invention is, therefore, to provide a removable return bend of simple and cheap construction, capable of maintaining a fluid tight joint at high temperatures and under high pressures.

l. between the ends of the pipes 10 the ends of the bend 14, the ends of the pipes With this and other objects in View. the invention consists in the return bend lconnection described in the follOWing specification and defined in the claim.

The various features of the invention are illustrated in the accompanying drawings, in which:

Fig. 1 is an end view of a return bend rnbodying the preferred form of the invenion;

Fig. 2 is a side view partly in section of the return bend showing the connection of the bend with the ends of the heating tubes or pipes; and

Fig. 3 is a detail sectional view showing the arrangement of the return bend and heating pipes and illustrating the use of a ferrule of copper or soft metal to facilitate the formation of a fluid tight joint.

In the accompanying drawings, the ends of steel heating tubes 10 and 12 projecting beyond the furnace wall are connected to each other by means of a cast iron bend 14, the open ends of which are fitted to the ends of the pipes 10 and 12 to form a passageway from one pipe to the other. To form an easily disconnectable and fluid tight joint and 12 and are provided with a bevelled outer surface 16 and the corresponding inner wall of the ends of the bend 14 are provided with an outwardly flared beveled surface 18 substantially parallel with the surface 16 of the pipe. The angle of the bevels 16 and 18 have an important bearing on the tightness and strength of a joint which may be made. For high temperature and high pressure joints an angle of 15 has been found to be very satisfactory.

Then the pipes are forced into the ends vof the bend under a moderately high pressure, the faces 16 and 18 are wedged together under a very high contact pressure due to the gradual slope of the faces to the direction of the force. The face 16 of the pipe is forced to conform to the inner surface 18 and the formation of passageways or leaks through the joint is thereby avoided. To hold the pipes 10 and 12 in a fluid tight engagement with the ends of the bend 14, the bend and pipes are clamped together by means of bolts. Accordingly, lugs 22 and 24 are formed 'on the bend 14 which are provided with holes arranged to receive bolts lut llt

26, 28, 30 and 32. The holes in lugs 22 and 24 are set relatively close to the main opening or conduit through the bend 14 so as to economize space and the lugs 22 and 24 are run up away fromthe mouths of the bend in straight lines perpendicular to the plane of the face of the mouths for such a distance that the nuts 27 on the ends of the bolts 26, 28, 30 andv 32 may be turned up tight against the ends of the lugs 22 and 24 without interference in the turning of the nuts from the outer surface of the main body of the bend. The arrangement just mentioned not only permits the ready tightening of the nuts 27 and economizes space, but it results in carrying the lugs 22 and 24 to a distance removed from the mouths of the bend such that pronounced shoulders 25 are formed on the outer surfaces of the bend connecting the lugs 22 and 24-in pairs. The shoulders 25 not only render the casting of the complete bend a more facile operation, but also considerably strengthen the structure of the bend as a whole. Collars 34 and 36 are mounted on the ends of the pipes 10 and 12 and openings are formed in the collars arranged to receive the bolts 26, 28. 3() and 32. The collars 34 and 36 are internally threaded and the pipes 10 and 12 are provided with corresponding threads 38 to permit the position of the collars to be adjusted to the lengths of the bolts 26 to 32.

When the end of the pipe 10 is forced into the end of the bend 14 the face 16 contacts throughout its entire surface with the inner face 18 of the bend and because of this eX- tended contact surface and the heavy contact pressure between the surfaces, it is not necessary to grind the surfaces 16 and 18. A fluid tight joint will be produced when the surfaces are merely machined. With pressures above about 80 pounds per square inch,

however, a fluid tight joint will not be obtained with machined surfaces without putting an excessive strain on the lugs 22 and Y the bolts 26 and 28. When very high pressures are used, therefore, a ferrule 40 of copper or other comparativelysoft metal is `inserted between the surfaces 16 and 18, as indicated in Fig. 3. As the faces 16 and 18 are forced together, the ferrule will act as i a cushion or liller between the surfaces and enable a tight joint to be obtained without putting an excessive strain on the fittings.

Inasmuch as no packing other than the copper ferrule is used in the bend connection, the bend may be used at any temperatures which the metal forming the coil will withstand. In addition, the bend is so constructed that it may be easily and quick- 1y disconnected from the heatingl tubes and may be quickly reassembled.v Inasmuch as the machined, bevelled surface 16 is on the outer face of the tube, the danger of scratching or marring this surface by the cleaning tubes inserted into the pipe 10 is avoided. The bend is, moreover, of a very cheap and simple construction, making it suitable where frequent changes or readjustments in the apparatus are necessary.

One of the important advantages of the structure herein disclosed has manifest itself in actual practice and follows from the fact that the bolts 2 6. 28, 30 and 3 2 all have their bodies substantialy enclosed andproteeted by the metal of the lugs 22 and 24 and the {ianges 34 and 36 from contact with heated gases surrounding the bend 14 and the tubes 10 and 12, onlv the heads of the bolts and the extreme ends of the bodies being materially exposed. It will be seen that the flanges 34 and 36 are set for this purpose, 'quite close to the mouths of the coupling 14 and that the anges and lugs completely enclose the bodies of the bolts throughout the length of the flanges and lugs. As-a result of this arrangement the metal of the flanges and lugs is always at a higher temperature when the devices are in use than that of the bodies of the bolts. Consequently a high temperature on the exterior of the coupling and to which it might be subjected when used in a water tube boiler or in case of fire from oil leaks in the joints of a pipe still serves merely to expand the metal of the lugs and thus increase the pressures on the joints between the tubes 10 and 12 and the return bend 14.

While the bend has been described as used in connection with a tubular oil still, it may be used in many other types of apparatus where two portions of pipe are to be connected by abend.

Having described the invention, what is claimed as new is:

A return bend for pipe stills having a curved body forming a conduit, the ends of said conduit lying substantially in a given plane, a pair of apertured lugs fixed to said odynear each end thereof, the lugs of each pair lying on opposite sides of the respective ends of the bend and having their apertures closely adjacent the respective mouths of the conduit, said lugs of each pair extending in a straight line along the body of the bend and a pronounced shoulder on the outer surface of the body of the bend connecting the lugs of each pair at their ends remote from the mouths of said conduit.

In testimony whereof I aiix my signature.

JAMES P. FISHER. 

